I have noticed when I try to adjust the diopter settings of my Denk II Binoviewer when it gets below 20 or so degrees it really gets stiff and almost impossible to rotate the eyepieces to achieve equal focus.

Have others run into this issue? And if so is ther a way to replace the lubricant to something that remains viscous in the extreme cold weather?

Just came in from a 2 deg F observing session and the diopters as well as the pupil spread mechanisim were nearly impossible to move.

The only issue I ever had with any astronomy equipment was with Meade UWA 5000 series eyepieces, where the grease freezes, and gets stuck in that position, till you bring eyepieces inside to warm up. Hence I fuly extend them when it is cold so they are good to observe.